Military Assault Command Operations, or MACO (pronounced "MAY-ko") for short, was a Terran Empire military organization in service during the 2150s. MACOs served aboard Starfleetstarships and could hold positions at least as high as first officer.

After Enterprise was destroyed while the USS Defiant was captured from the Tholians, MACOs were used to interrogate the alien slave labors about acts of sabotage, committed by the GornslavemasterSlar. MACOs were also responsible for the hunt to kill Slar in the Defiant's secondary hull, and several of them were killed or wounded before he was captured and killed by Archer.

Their weapon seems very similar to an XM8 modular battle rifle in function and size, including the marksman variant seen in "The Xindi". The rifle in sniper mode also bears a strong resemblance to the Federation sniper rifle from the Star Trek: Voyager - Elite Force video games, which preceded Enterprise.

The mirror universe mission patch was a skull. This star and skull symbol is reminiscent of the World War II US Marine Raiders patch. Their motto was "Ever Invincible."